Stenciling machine



Dec. 30, 1952' w. P. MCCORMICK ET AL 3,

STENCILING MACHINE Filed on. 7, 1948 2 SHEETS-SHEET v1 f I We gJa/L 14W; Attorney 3 Dec. 30, 1952 Filed Oct. 7, 1948 W. P. M CORMICK ET AL STENCILING MACHINE 2 SHEETS--SHEET 2 Inventor WILL IA M Hm PMc CORN/CK Foes-T GE/qHA M/IL. 50M

:ZMM a4...) wax 1 7 Attorney 5 Patented Dec. 30, 1952 STENOILING MACHINE William Philip McCormick, Glasgow, and Robert Graham Wilson, Cardross, Scotland Application October 7, 1948, Serial No. 53,234 In Great Britain March 24, 1948 7 Claims.

This invention relates to a stencilling machine for stencilling paint, paste or ink on to paper, board, glass and the like (hereinafter referred to as the sheets to be printed) through a prepared gauze stencil by means of a travelling squeegee or scraper.

More especially, the invention relates to a stencilling machine of power-operated type comprising a supporting table to which are fed the sheets to be printed, a pivotal frame for the gauze fabric screen to which a stencil is applied and a squeegee pivoted to a carrier that is reciprocable on said frame to perform forward working strokes and return strokes, the squeegee being engageable with the screen when loweredupon the table during the forward working strokes in order to spread printing material over and press it through the stencil screen.

An object of the invention is to provide in such a machine a power-operated crank rotating in a vertical plane about a horizontal axis, a connecting-rod pivotally connected at opposite ends to said crank and to the squeegee, the arrangement being such that during each working stroke the connecting-rod pushes the squeegee forwards and during each return stroke the connectingrod pulls the squeegee rearwards, a pivotal connection incorporating a lost-motion device between the connecting-rod and the carrier, and additional power-operated means which during each return stroke of the squeegee acts, firstly, to 'lift the frame for a predetermined period of time in order to expose the table for the sheetfeeding operation, the period of time available in the cycle of operations for said lifting operation being extended beyond the end of the return stroke by the action of the lost-motion device at said end, and secondly, to control the lowering of the frame towards the table for the next forward working stroke.

Another obiect is to incorporate the lost-motion device in the pivotal connection between the connecting-rod and the carrier to ensure that the forward push of the connecting-rod will be translated into forceful downward pressure of the squeegee on the table-supported screen and to arrange that the connecting-rod pushes the scrueegee at a downward inclination so as to assist in holding the frame down upon the table against the reaction thereof on the squeegee.

Other obiects of the invention will be apparent from the fo lowing specification and claims.

An embodiment of the invention will now be described. by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a side elevation of the stencilling ma-- chine,

Fig. 2 is a plan view corresponding to Fig. 1,

Fig. 3 is a detail side elevation of part of the machine,

Fig. 4 is a fragmentary end view in the direction of the arrow in Fig. 3, and

Fig. 5 is a view corresponding to Fig. 3, showing the part in a different position.

Fig. 6 is a section on the line 6-6 of Fig. 2.

Referring to Figs. 1 and 2, the machine is driven by an electric motor A, as shown, or by suitable alternate means, through a V-rope drive B to a worm reducing gear box I and thence to a shaft 2.

A train of gears 3, 4 and 5 on horizontal shafts 2, 6 and 1 respectively continues the drive, and the shaft I has fixed at each extremity a driving disc 8 having a pin 8A which serves as a crank rotating in a vertical plane. During the rotation of the discs 8, their cranks BA transmit simultaneous reciprocating motion to carrier members or blocks 9 by means of drive-connecting members or connecting rods ID.

The shafts 2, 6 and l are journalled one above another in upright members F of the machine frame F.

The blocks 9 are slidably mounted on guide bars I l which are pivotally mounted on the shaft 1, said blocks carrying the squeegee.

During the forward or working stroke, as Fig. 1 shows, the connecting rods I!) are arranged to push forwards at a downward inclination relative to the guide bars H. Throughout each working stroke the guide bars I I to which a frame l2 carrying a stencilled gauze screen I3 is fixed. are supported on a printing table I as shown in full lines in Fig. 1. It is the table I4 which receives the sheets to be printed.

During the back or non-working stroke, the connecting rods H] are arranged to pull rearwards at a downward inclination relative to the guide bars H. During the first portion of the nonworking stroke, the guide bars ll together with the frame 12 and stencil 13 are elevated to the position shown diagrammatically in chain dotted lines in Fig. l, by the action of cams or rollers IS on levers I 6. The arrangement of the connecting rods it! to push downwards and also pull downwards is gotten by locating the crank-disc shaft 1 approximately in the plane of the printing table M.

The rollers I5 project laterally from, and are freely rotatable on pins fixed to discs I! which are mounted on and rotate with the shaft 5, and

the rollers I5 are so positioned on the discs I! that they make contact with levers I6 when the blocks 9 are at the end of each forward or working stroke.

The levers I6 are attached to the guide bars II so as to give the required elevation to the guide bars II, frame I2 and stencil I3 and allow them to lower again to rest on the table I4 at the end of the non-working stroke.

During the period of elevation the printed sheet is removed by hand and a fresh sheet to be printed is placed in position on table l4 in preparation for the next working stroke.

The action of the squeegee during the working and non-working strokes is shown in more detail in Figs. 3 and 5 which for convenience are located horizontally on the sheet.

Fig. 3 shows a side elevation of the sliding carrier blocks 9 during a forward or working stroke. A cross-member or rod I8 interconnects the ends of the connecting rods I and is pivotally mounted therein, each end portion of the rod passing through a slot IBA in each block. In effect, the end portions of the rod I8 and the slots ISA form pin-and-slot connections between the rods Ill and blocks 9 (see also Fi Each slot IBA is elongated in the direction of travel of the block and the rod I8 is slidable in the slots. It will be obvious that the connection between the connecting rods II) and the carrier blocks 9 through the cross-rods I8 and slots I8A is a lost-motion device. That is to say, at the start of each push (or pull) of the connecting rods, the cross rod I8 will move forwards (or rearwards) to the then opposite end of the slots before the blocks start their stroke. A second cross-member or rod I9 is provided which extends between and is fixedly secured at each end to the carrier blocks 9, and assists the blocks to maintain correct alignment with each other.

The squeegee 2D fulcrums about a rod 2| the ends of which are mounted in the blocks 9, and vertical adjustment of the squeegee is provided by bolts 22 and nuts 22A.

Thus, during the forward or working stroke of the connecting rods II), the rod I8 pushes the squeegee 20, pivoting it about its fulcrum and pressing its lower end on to the gauze I3. By virtue of the lost-motion device I3, NBA, and the low point of application of the thrust of the connecting rods I0 below the fulcrum 2|, as Fig. 3 shows, the connecting rods II] can push the squeegee very hard upon the screen, which of course is supported by the table It below. The reaction to the downthrust of the squeegee 28 is transmitted through the fulcrum 2| to the carrier blocks 9 and thence to the frame I I I 2.

Fig. 5 shows a view corresponding to Fig. 3, but during a backward or non-working stroke. The squeegee 20 is lifted cellar of the gauze stencil I3 by the rod I8, which moves back along elongated slots I8A provided in the blocks 9 and the rod I8 is attached to the squeegee 2! by clips 23 so that the squeegee is caused to pivot about the rod ZI and lift the squeegee clear of the stencil I3.

When the rod I8 has taken up the total backward travel allowed by the elongated slots IBA, as shown in Fig. 5, it then drives the blocks 9 on the backward or non-working stroke at the end of which the action described above is reversed and the position shown in Fig. 3 is resumed. At the start of the next forward stroke, the already described lost-motion effect in the device I8, I8A occurs, thus delaying the actual start of the squeegees working stroke in relation to the crank discs 8. The arrangement of the crank-and-connecting-rod mechanism in combination with the action of the lost-motion device is such that an appreciable period occurs between the end of the return stroke and the re-start of work by the squeegee, such period being an extension of the period available for the hand-feed operation.

It will be understood that the pressure of the squeegee 20 on the gauze stencil I3 during the working stroke stencils the ink, paint or paste through the gauzestencil I3 on to the sheet on the table I4.

Extensions of the guide bars I I support a counterweight (3. However, as will be understood, the distribution of weight in the pivotal frame I2 and its associated parts is such that they are biassed to bear upon the table I 4. The action of the mechanism 4, I5, I6 is positive in one direction only, namely the direction in which it elevates the frame to the chain-dot position in Fig. 1. As regards lowering of the frame, this is gravi- 1 tational, being due to the bias referred to, al-

though normally under the control of the mechanism 4, I5, I6. Thus, should the operator fail to do the hand-feed operation in time, he can hold up the frame and there is no danger of accident to his hands.

It has already been shown that the upward reaction to the forcible down-thrust by the saucegee 28 during its working stroke is transmitted through the fulcrum 2| and carrier blocks 9 to the frame I I, I2. It will be appreciated that the frame opposes the reactive upthrust under its downward gravitational bias assisted by the downwardly inclined thrust of the connecting rods l!) during the working stroke.

We claim:

1. In a stencilling machine of power-operated type comprising a supporting table to which are fed the sheets to be printed, a pivotal frame for a fabric screen to which a stencil is applied. a carrier reciprocable on said frame to perform forward working strokes and return strokes, and a squeegee pivotally connected to said carrier, said squeegee being engageable with the screen during the forward working strokes in order to spread printing material over and press it through the stencil screen; the combination of a power-operated crank rotating in a vertical plane about a horizontal axis, a connecting-rod pivotally connected at opposite ends to said crank and to the carrier and squeegee, the arrangement bevice incorporated in the pivotal connection between the connecting-rod and the carrier, and additional power-operated means which during each return stroke of the squeegee acts, firstly,

to lift the frame for a predetermined period of time in order to expose the table for the sheetfeeding operation, the period of time available in the cycle of operations for said lifting operation being extended beyond the end of thereturn stroke by the action of the lost-motion device at said end, and secondly, to control the lowering of the frame towards the table for the next for-' ward working stroke.

2. In a stencilling machine according to claim 1, in which the pivotal frame is biassed downwards, the arrangement of the crank and connecting-rod so that during the forward working stroke the connecting rod pushes at a downward inclination to press the squeegee upon the stencilled screen and also to assist the bias on the frame in holding the frame down upon the table against the reaction thereof on the squeegee.

3. In a stencilling machine according to claim 1, lever means rigidly connected to the pivotal frame and projecting downwardly therefrom and cam means which is rotated in conjunction with the crank and which operates the lever means during the return stroke of the squeegee to positively raise the frame clear of the supporting table and allow the frame to lower freely by gravity under control of the cam means.

4. In a stencilling machine of power-operated hand-feed type comprising a supporting table to which are fed the sheets to be printed, a pivotal frame for a fabric screen to which a stencil is applied, a carrier reciprocable on said frame to perform forward working strokes and return strokes, and a squeegee pivotally connected to said carrier, said squeegee being engageable with the screen during the forward working strokes in order to spread printing material over and press it through the stencilled screen; the combination of a power-operated crank rotating in a vertical plane about a horizontal axis, a connecting-rod pivotally connected at opposite ends to said crank and to the carrier and squeegee, a lost-motion device incorporated in the pivotal connection between the connecting-rod and the carrier by virtue of which device the squeegee can be forced by the connecting-rod to press hard upon the stencil screen, the arrangement of the crank and connecting-rod being such that during each working stroke the connecting-rod pushes forwards on the squeegee at a downward inclination to assist in holding the frame down upon the table and during each return stroke the connecting-rod pulls the squeegee rearwards, and additional power-operated means which during each return stroke of the squeegee acts, firstly, to lift the frame in order to expose the table for the sheet-feeding operation, and secondly, to control the lowering of the frame towards the table for the next forward working stroke.

5. In a stencilling machine of power-operated type comprising a supporting table for the sheets to be printed, a pivotal frame for a fabric screen to which a stencil is applied, a carrier slidably mounted on said frame and reciprocable to perform forward working strokes and return strokes, a squeegee depending from said carrier and being engageable at an acute angle with the screen during the forward working strokes in order to spread printing material over and press it through the stencil screen and a pivot between the squeegee and carrier: the combination of a power-operated push-pull rod connected directly to the squeegee at a level below the pivot thereof and a pin-and-slot connection between the squeegee and the carrier, said push-pull rod being so arranged that during each working stroke it pushes at a downward inclination, the push being imparted to the squeegee and to the carrier and frame so as to flex the squeegee hard down on the screen and also assist in holding the frame upon the supporting table against the reaction thereof on the squeegee.

6. In a stencilling machine of power-operated type comprising a supporting table to which are fed sheets to be printed, a pivotal frame for a fabric screen to which a stencil is applied, a carrier slidably mounted on said frame and reciprocable to perform forward working strokes and return strokes, means for raising and lowering said frame during each return stroke and a squeegee depending pivotally from said carrier and being engageable at an acute angle with the screen during the forward working strokes in order to spread printing material over and press it through the stencil screen; a power-operated crank rotating in a vertical plane, a cross-rod connected to the squeegee at a level below the pivot thereof and having a lost-motion connection with said carrier and a connecting-rod pivotally connected at opposite ends to said crank and to said cross-rod, the arrangement being such that during each working stroke the connecting-rod pushes at a downward inclination both on the squeegee and on the carrier so as to flex the squeegee hard upon the screen and also assist in holding the frame down upon the supporting table against the reaction thereof on the squeegee and during each return stroke the connecting-rod pulls the squeegee clear of the screen.

7. In a stencilling machine of power-operated type comprising a supporting table to which are fed the sheets to be printed, a pivotal frame for a fabric screen to which a stencil is applied, said frame being downwardly biased to bear upon said table, a carrier slidably mounted. on said frame and reciprocable to perform forward working strokes and return strokes and a squeegee depending pivotally from said carrier and being engageable at an acute angle with the screen during the forward working strokes in order to spread printing material over and press it through the stencil screen; a shaft on which said frame is pivotally mounted, said shaft being located approximately in the plane of said table, a power-operated crank rotating in a vertical plane about said shaft as axis, a cross-rod connetcted to the squeegee at a level below the pivot thereof and having a lost-motion connection with said carrier, a connecting-rod pivotally connected at opposite ends to said crank and to said cross-rod, the arrangement being such that during each working stroke the connecting-rod pushes at a downward inclination both on the squeegee and on the carrier and frame so as to flex the squeegee hard down on the screen and also assist the downward bias to hold the frame upon the supporting table and during each return stroke the connecting-rod pulls the squeegee pivotally clear of the screen, and additional power-operated means which during each return stroke acts, firstly, to lift the frame in order to expose the table for the sheet feeding operation, and second- 1y, to allow the frame to lower under its bias upon the table for the next forward working stroke.

WILLIAM PHILIP McCORMICK. ROBERT GRAHAM WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

